1 /* DTLS implementation written by Nagendra Modadugu 2 * (nagendra (at) cs.stanford.edu) for the OpenSSL project 2005. */ 3 /* ==================================================================== 4 * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 18 * 3. All advertising materials mentioning features or use of this 19 * software must display the following acknowledgment: 20 * "This product includes software developed by the OpenSSL Project 21 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 22 * 23 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 24 * endorse or promote products derived from this software without 25 * prior written permission. For written permission, please contact 26 * openssl-core (at) openssl.org. 27 * 28 * 5. Products derived from this software may not be called "OpenSSL" 29 * nor may "OpenSSL" appear in their names without prior written 30 * permission of the OpenSSL Project. 31 * 32 * 6. Redistributions of any form whatsoever must retain the following 33 * acknowledgment: 34 * "This product includes software developed by the OpenSSL Project 35 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 38 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 40 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 43 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 44 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 45 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 46 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 47 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 48 * OF THE POSSIBILITY OF SUCH DAMAGE. 49 * ==================================================================== 50 * 51 * This product includes cryptographic software written by Eric Young 52 * (eay (at) cryptsoft.com). This product includes software written by Tim 53 * Hudson (tjh (at) cryptsoft.com). 54 * 55 */ 56 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 57 * All rights reserved. 58 * 59 * This package is an SSL implementation written 60 * by Eric Young (eay (at) cryptsoft.com). 61 * The implementation was written so as to conform with Netscapes SSL. 62 * 63 * This library is free for commercial and non-commercial use as long as 64 * the following conditions are aheared to. The following conditions 65 * apply to all code found in this distribution, be it the RC4, RSA, 66 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 67 * included with this distribution is covered by the same copyright terms 68 * except that the holder is Tim Hudson (tjh (at) cryptsoft.com). 69 * 70 * Copyright remains Eric Young's, and as such any Copyright notices in 71 * the code are not to be removed. 72 * If this package is used in a product, Eric Young should be given attribution 73 * as the author of the parts of the library used. 74 * This can be in the form of a textual message at program startup or 75 * in documentation (online or textual) provided with the package. 76 * 77 * Redistribution and use in source and binary forms, with or without 78 * modification, are permitted provided that the following conditions 79 * are met: 80 * 1. Redistributions of source code must retain the copyright 81 * notice, this list of conditions and the following disclaimer. 82 * 2. Redistributions in binary form must reproduce the above copyright 83 * notice, this list of conditions and the following disclaimer in the 84 * documentation and/or other materials provided with the distribution. 85 * 3. All advertising materials mentioning features or use of this software 86 * must display the following acknowledgement: 87 * "This product includes cryptographic software written by 88 * Eric Young (eay (at) cryptsoft.com)" 89 * The word 'cryptographic' can be left out if the rouines from the library 90 * being used are not cryptographic related :-). 91 * 4. If you include any Windows specific code (or a derivative thereof) from 92 * the apps directory (application code) you must include an acknowledgement: 93 * "This product includes software written by Tim Hudson (tjh (at) cryptsoft.com)" 94 * 95 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 96 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 97 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 98 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 99 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 100 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 101 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 102 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 103 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 104 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 105 * SUCH DAMAGE. 106 * 107 * The licence and distribution terms for any publically available version or 108 * derivative of this code cannot be changed. i.e. this code cannot simply be 109 * copied and put under another distribution licence 110 * [including the GNU Public Licence.] */ 111 112 #include <openssl/ssl.h> 113 114 #include <assert.h> 115 #include <string.h> 116 117 #include <openssl/bytestring.h> 118 #include <openssl/err.h> 119 120 #include "internal.h" 121 122 123 /* to_u64_be treats |in| as a 8-byte big-endian integer and returns the value as 124 * a |uint64_t|. */ 125 static uint64_t to_u64_be(const uint8_t in[8]) { 126 uint64_t ret = 0; 127 unsigned i; 128 for (i = 0; i < 8; i++) { 129 ret <<= 8; 130 ret |= in[i]; 131 } 132 return ret; 133 } 134 135 /* dtls1_bitmap_should_discard returns one if |seq_num| has been seen in |bitmap| 136 * or is stale. Otherwise it returns zero. */ 137 static int dtls1_bitmap_should_discard(DTLS1_BITMAP *bitmap, 138 const uint8_t seq_num[8]) { 139 const unsigned kWindowSize = sizeof(bitmap->map) * 8; 140 141 uint64_t seq_num_u = to_u64_be(seq_num); 142 if (seq_num_u > bitmap->max_seq_num) { 143 return 0; 144 } 145 uint64_t idx = bitmap->max_seq_num - seq_num_u; 146 return idx >= kWindowSize || (bitmap->map & (((uint64_t)1) << idx)); 147 } 148 149 /* dtls1_bitmap_record updates |bitmap| to record receipt of sequence number 150 * |seq_num|. It slides the window forward if needed. It is an error to call 151 * this function on a stale sequence number. */ 152 static void dtls1_bitmap_record(DTLS1_BITMAP *bitmap, 153 const uint8_t seq_num[8]) { 154 const unsigned kWindowSize = sizeof(bitmap->map) * 8; 155 156 uint64_t seq_num_u = to_u64_be(seq_num); 157 /* Shift the window if necessary. */ 158 if (seq_num_u > bitmap->max_seq_num) { 159 uint64_t shift = seq_num_u - bitmap->max_seq_num; 160 if (shift >= kWindowSize) { 161 bitmap->map = 0; 162 } else { 163 bitmap->map <<= shift; 164 } 165 bitmap->max_seq_num = seq_num_u; 166 } 167 168 uint64_t idx = bitmap->max_seq_num - seq_num_u; 169 if (idx < kWindowSize) { 170 bitmap->map |= ((uint64_t)1) << idx; 171 } 172 } 173 174 enum ssl_open_record_t dtls_open_record( 175 SSL *ssl, uint8_t *out_type, uint8_t *out, size_t *out_len, 176 size_t *out_consumed, uint8_t *out_alert, size_t max_out, const uint8_t *in, 177 size_t in_len) { 178 CBS cbs; 179 CBS_init(&cbs, in, in_len); 180 181 /* Decode the record. */ 182 uint8_t type; 183 uint16_t version; 184 uint8_t sequence[8]; 185 CBS body; 186 if (!CBS_get_u8(&cbs, &type) || 187 !CBS_get_u16(&cbs, &version) || 188 !CBS_copy_bytes(&cbs, sequence, 8) || 189 !CBS_get_u16_length_prefixed(&cbs, &body) || 190 (ssl->s3->have_version && version != ssl->version) || 191 (version >> 8) != DTLS1_VERSION_MAJOR || 192 CBS_len(&body) > SSL3_RT_MAX_ENCRYPTED_LENGTH) { 193 /* The record header was incomplete or malformed. Drop the entire packet. */ 194 *out_consumed = in_len; 195 return ssl_open_record_discard; 196 } 197 198 if (ssl->msg_callback != NULL) { 199 ssl->msg_callback(0 /* read */, 0, SSL3_RT_HEADER, in, 200 DTLS1_RT_HEADER_LENGTH, ssl, ssl->msg_callback_arg); 201 } 202 203 uint16_t epoch = (((uint16_t)sequence[0]) << 8) | sequence[1]; 204 if (epoch != ssl->d1->r_epoch || 205 dtls1_bitmap_should_discard(&ssl->d1->bitmap, sequence)) { 206 /* Drop this record. It's from the wrong epoch or is a replay. Note that if 207 * |epoch| is the next epoch, the record could be buffered for later. For 208 * simplicity, drop it and expect retransmit to handle it later; DTLS must 209 * handle packet loss anyway. */ 210 *out_consumed = in_len - CBS_len(&cbs); 211 return ssl_open_record_discard; 212 } 213 214 /* Decrypt the body. */ 215 size_t plaintext_len; 216 if (!SSL_AEAD_CTX_open(ssl->aead_read_ctx, out, &plaintext_len, max_out, 217 type, version, sequence, CBS_data(&body), 218 CBS_len(&body))) { 219 /* Bad packets are silently dropped in DTLS. See section 4.2.1 of RFC 6347. 220 * Clear the error queue of any errors decryption may have added. Drop the 221 * entire packet as it must not have come from the peer. 222 * 223 * TODO(davidben): This doesn't distinguish malloc failures from encryption 224 * failures. */ 225 ERR_clear_error(); 226 *out_consumed = in_len - CBS_len(&cbs); 227 return ssl_open_record_discard; 228 } 229 230 /* Check the plaintext length. */ 231 if (plaintext_len > SSL3_RT_MAX_PLAIN_LENGTH) { 232 OPENSSL_PUT_ERROR(SSL, SSL_R_DATA_LENGTH_TOO_LONG); 233 *out_alert = SSL_AD_RECORD_OVERFLOW; 234 return ssl_open_record_error; 235 } 236 237 dtls1_bitmap_record(&ssl->d1->bitmap, sequence); 238 239 /* TODO(davidben): Limit the number of empty records as in TLS? This is only 240 * useful if we also limit discarded packets. */ 241 242 *out_type = type; 243 *out_len = plaintext_len; 244 *out_consumed = in_len - CBS_len(&cbs); 245 return ssl_open_record_success; 246 } 247 248 int dtls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out, 249 uint8_t type, const uint8_t *in, size_t in_len, 250 enum dtls1_use_epoch_t use_epoch) { 251 /* Determine the parameters for the current epoch. */ 252 uint16_t epoch = ssl->d1->w_epoch; 253 SSL_AEAD_CTX *aead = ssl->aead_write_ctx; 254 uint8_t *seq = ssl->s3->write_sequence; 255 if (use_epoch == dtls1_use_previous_epoch) { 256 /* DTLS renegotiation is unsupported, so only epochs 0 (NULL cipher) and 1 257 * (negotiated cipher) exist. */ 258 assert(ssl->d1->w_epoch == 1); 259 epoch = ssl->d1->w_epoch - 1; 260 aead = NULL; 261 seq = ssl->d1->last_write_sequence; 262 } 263 264 if (max_out < DTLS1_RT_HEADER_LENGTH) { 265 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL); 266 return 0; 267 } 268 /* Check the record header does not alias any part of the input. 269 * |SSL_AEAD_CTX_seal| will internally enforce other aliasing requirements. */ 270 if (in < out + DTLS1_RT_HEADER_LENGTH && out < in + in_len) { 271 OPENSSL_PUT_ERROR(SSL, SSL_R_OUTPUT_ALIASES_INPUT); 272 return 0; 273 } 274 275 out[0] = type; 276 277 uint16_t wire_version = ssl->s3->have_version ? ssl->version : DTLS1_VERSION; 278 out[1] = wire_version >> 8; 279 out[2] = wire_version & 0xff; 280 281 out[3] = epoch >> 8; 282 out[4] = epoch & 0xff; 283 memcpy(&out[5], &seq[2], 6); 284 285 size_t ciphertext_len; 286 if (!SSL_AEAD_CTX_seal(aead, out + DTLS1_RT_HEADER_LENGTH, &ciphertext_len, 287 max_out - DTLS1_RT_HEADER_LENGTH, type, wire_version, 288 &out[3] /* seq */, in, in_len) || 289 !ssl3_record_sequence_update(&seq[2], 6)) { 290 return 0; 291 } 292 293 if (ciphertext_len >= 1 << 16) { 294 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); 295 return 0; 296 } 297 out[11] = ciphertext_len >> 8; 298 out[12] = ciphertext_len & 0xff; 299 300 *out_len = DTLS1_RT_HEADER_LENGTH + ciphertext_len; 301 302 if (ssl->msg_callback) { 303 ssl->msg_callback(1 /* write */, 0, SSL3_RT_HEADER, out, 304 DTLS1_RT_HEADER_LENGTH, ssl, ssl->msg_callback_arg); 305 } 306 307 return 1; 308 } 309
